Code review comment for ~ltrager/maas:lp1813019

Before the random number generator happened to create a value big enough for tests to pass. The failure in 5491 happened because it generated a number to small. If you look at the stack trace in 5491 you can see its failing in the VMFS6Layout.clean(). I could remove that fix and keep trying to land until it generates a large enough number but we'd still have the same problem.